1. Field of the Invention
The present invention relates to a technology for controlling a route to be used in a network.
2. Description of the Related Art
Conventionally, a network design that improves the reliability of the network by connecting a center router with a base router using the network including plural carriers has been implemented. FIG. 23 illustrates a configuration having a duplicated carrier. In the configuration shown in FIG. 23, carrier services respectively having different contents for cost and band guarantee are combined to optimize a routing information protocol (ROI).
1. A service of a carrier A is assumed to be a service for which the cost is high and the band can not be widened, however, the band is guaranteed. 2. A service of a carrier B is assumed to be a service for which the cost is low and a wide band can be expected, however, the band is not guaranteed (best-effort type). By combining these two carriers respectively having different service contents, a network that guarantees the minimum band, can be expected a wide band, and is reliable as a whole, can be designed at a reasonable cost.
A center router 100 and base routers 101, in a network of a form formed by combining a plurality of these carriers, communicate communication data between the center side and the base side using either of the plurality of carrier lines A and B according to the situation. As a technique close to this configuration, multi-homing that connects the connection with the Internet using plural internet service provider (ISP) lines can be listed (for example, Japanese Patent Laid-Open No. 2005-57487).
According to the above configuration, both of the center router 100 and the base routers 101 distribute the load corresponding to the load state of the connection lines of the carriers A and B to which the center router 100 and the base router 101 are connected. For example, the load state of the connection line of a router is always monitored and new communication is executed using the carrier A or B having a smaller load. This new communication is executed in packets, in combinations of hosts, in new sessions, etc.
However, data transmitted from the center side to the base side are distributed corresponding not to the load state of the lines on the base side but to the load state of the lines on the center side. In general, the lines on the center side are designed to have a band (line capacity) with sufficient availability. As described above, when the data are distributed corresponding to the load state of the lines on the center side, the optimal distribution by the center router 100 can not be realized because the load state of the lines on the base side can not be considered.
In another distribution method, the distribution ratio for data from the center router 100 to the base routers 101 is fixedly determined. In this method, although distribution considering the difference in the contracted band of the connection lines between the carriers A and B of the base routers 101 is enabled, the optimal distribution corresponding to the actual state of the connection lines of the carriers of the base routers 101 can not be realized. Especially when the carriers A and B respectively having a service conflicting with each other as in the items 1 and 2 above are selected, the distribution is insufficient when the distribution is formed only by assigning fixedly in advance because any fixed value can not be guaranteed in the band on the lines of the carrier B.